Originally Posted by elp_jc
It does NOT monitor crap buddy
. There's no oil condition sensor (there're quite expensive, and only monitor oil viscosity on some big rigs); it's just an algorithm, like all other cars. Reset it at any point and it'd go another 15K miles
. And as all such algorithms, it starts to count down slow initially, and quicker when you approach zero.
There IS an oil condition sensor. There is a pdf on this site that explains how it works. Maybe it isn't as advanced as you would like, but it is attempting to measure oil quality on some level.
My car has never gone the full 15k before it told me to change it - because I drive it hard...most days.